热影响区软化焊接接头的强度及变形

焊接接头热影响区软化是细晶粒钢焊接时普遍存在的问题。用有限元分析方法，分析热影响区软化的焊接接头屈服强度和抗拉强度，以及接头上的应力分布和变形机制。分析结果表明，软化热影响区的屈服应力降低和宽度增加对接头的屈服强度降低影响较小，而对接头抗拉强度降低影响较大，提高焊缝的屈服应力可以提高热影响区软化接头强度。同时发现，当外加应力超过软化热影响区的屈服应力时，在热影响区及其附近区域出现了三轴应力状态．主应力及Mises等效应力在有屈服应力差别的区域交界处发生突变，使热影响区的Mises等效应力降低，与之相邻区域的Mises等效应力升高，从而可以对软化热影响区宽度及软化程度影响焊接接头强度的机制进行解释。

Strength and deformation in HAZ-softened welded joints

The softening in the HAZ(heat-affected zone) of the weldment of fine-grained steels is an ubiquitous problem. Using (he finite element analysis, both yield strength and tensile strength in the HAZsoftened welded joints are evaluated, and the stress distribution and deformation behaviors were analyzed. An calculation results show that an increase of the softened HAZ width and a decrease of yield stress in it can lower slightly yield strength m HAZsoftened joints, and reduced significantly the tensile strength in HAZsoftened joints. Increasing of the yield stress of weld metal can improve the yield strength and tensile strength in HAZ-softened welded joints. Analyses demonstrate that as applied stress is higher the yield stress of the softened HAZ, a triaxial stress state occurs in HAZ and its adjacent zones. At the boundaries of /ones with different yield stresses, the principal stresses and the Mises equivalent stresses change in the step wise. The Mises equivalent stresses decrease in the softened HA/ and increase in its adjacent zones correspondingly. Utilizing these analyses results, the mechanism of the effect of width and softened degree of softened -HAZ on the strength of such joints can be explained.